linux-kernel - Re: [PATCH] xfs: use kmem_cache_free() for kmem

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Date:   Tue, 12 Oct 2021 13:43:45 -0700
From:   "Darrick J. Wong" <djwong@...nel.org>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Rustam Kovhaev <rkovhaev@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Dave Chinner <david@...morbit.com>, linux-xfs@...r.kernel.org,
        cl@...ux.com, penberg@...nel.org, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, gregkh@...uxfoundation.org,
        Al Viro <viro@...iv.linux.org.uk>, dvyukov@...gle.com
Subject: Re: [PATCH] xfs: use kmem_cache_free() for kmem_cache objects

On Tue, Oct 12, 2021 at 01:43:20PM -0700, Darrick J. Wong wrote:
> On Sun, Oct 03, 2021 at 06:07:20PM -0700, David Rientjes wrote:
> > On Thu, 30 Sep 2021, Rustam Kovhaev wrote:
> > 
> > > > >> I think it's fair if something like XFS (not meant for tiny systems AFAIK?)
> > > > >> excludes SLOB (meant for tiny systems). Clearly nobody tried to use these
> > > > >> two together last 5 years anyway.
> > > > > 
> > > > > +1 for adding Kconfig option, it seems like some things are not meant to
> > > > > be together.
> > > > 
> > > > But if we patch SLOB, we won't need it.
> > > 
> > > OK, so we consider XFS on SLOB a supported configuration that might be
> > > used and should be tested.
> > > I'll look into maybe adding a config with CONFIG_SLOB and CONFIG_XFS_FS
> > > to syzbot.
> > > 
> > > It seems that we need to patch SLOB anyway, because any other code can
> > > hit the very same issue.
> > > 
> > 
> > It's probably best to introduce both (SLOB fix and Kconfig change for 
> > XFS), at least in the interim because the combo of XFS and SLOB could be 
> > broken in other ways.  If syzbot doesn't complain with a patched kernel to 
> > allow SLOB to be used with XFS, then we could potentially allow them to be 
> > used together.
> > 
> > (I'm not sure that this freeing issue is the *only* thing that is broken, 
> > nor that we have sufficient information to make that determination right 
> > now..)
> 
> I audited the entire xfs (kernel) codebase and didn't find any other
> usage errors.  Thanks for the patch; I'll apply it to for-next.

Also, the obligatory

Reviewed-by: Darrick J. Wong <djwong@...nel.org>

--D

> 
> --D